Closing a JFrame application can be done by setting the default close operation of the frame. There are some defined constant for the default operation. These constant includes EXIT_ON_CLOSE, HIDE_ON_CLOSE, DO_NOTHING_ON_CLOSE and DISPOSE_ON_CLOSE.
To exit an aplication we can set it to EXIT_ON_CLOSE, this option will call the System.exit() method when user initiate a close operation on the frame.
package org.kodejava.example.swing;
import javax.swing.JFrame;
public class MainFrameClose extends JFrame {
public static void main(String[] args) {
MainFrameClose frame = new MainFrameClose();
frame.setSize(100, 100);
//
// Be defining the default close operation of a JFrame to EXIT_ON_CLOSE
// the application will be exited by calling System.exit() when user
// initiate a close event on the frame.
//
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}